.\" Copyright (c) 1999
.\"	Nick Hibma <n_hibma@FreeBSD.org>. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\"
.Dd October 20, 2017
.Dt UDBP 4
.Os
.Sh NAME
.Nm udbp
.Nd USB Double Bulk Pipe driver
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device udbp"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
udbp_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides support for host-to-host cables
that contain at least two bulk pipes (one for each direction).
This typically includes cables branded for use with
.Sy Windows USB Easy Transfer ,
and many cables based on the Prolific PL2xx1 series of USB bridge chips.
A useful (but non-comprehensive) list of compatible USB host cables
is listed in the
.Sx SEE ALSO
section below.
.Pp
.\" XXX	The description of how to add netgraph to the kernel
.\"	is out of place here.  It should be limited to the
.\"	netgraph(4) manpage only.  However, that page does
.\"	not yet give instructions for kldload(8) for the
.\"	clueless.  Working on it -- sheldonh
It requires
.Xr netgraph 4
to be available.
This can be done either by adding
.Cd "options NETGRAPH"
to your kernel configuration file, or alternatively loading
.Xr netgraph 4
as a module, either from
.Pa /boot/loader.conf
or from the command line, before the
.Nm
module.
.Sh EXAMPLES
.Dl options NETGRAPH
.Dl device udbp
.Pp
Add the
.Nm
driver to the kernel.
.Pp
.Dl kldload netgraph
.Dl kldload udbp
.Pp
Load the
.Xr netgraph 4
module and then the
.Nm
driver.
.Pp
.Dl ngctl mkpeer udbp0: eiface data ether
.Dl ifconfig ngeth0 ether aa:dd:xx:xx:xx
.Dl ifconfig ngeth0 inet 169.254.x.x/16
.Pp
Create a new Ethernet network interface node
and connect its ether hook to the data hook of the
.Nm
driver.
.Pp
This enables FreeBSD to communicate with a Linux peer (e.g. using the
.Sy plusb
driver).
The Linux node should be configured to prefer link-local IPv4 addresses
(e.g. using Network Manager in Debian and Red Hat derived distributions).
.Pp
Whilst both FreeBSD and Linux are able to interoperate by
loosely following CDC EEM 1.0 in their behaviour, neither implementation
has been expressly designed to follow its specification.
.Sh SEE ALSO
.Xr netgraph 4 ,
.Xr ng_eiface 4 ,
.Xr ohci 4 ,
.Xr uhci 4 ,
.Xr usb 4 ,
.Xr ngctl 8
.\"
.Rs
.%B Universal Serial Bus: Communications Class Subclass Specification for Ethernet Emulation Model Devices
.%N Revision 1.0
.%D February 2, 2005
.%I USB Implementers Forum, Inc.
.%U http://www.usb.org/developers/docs/devclass_docs/CDC_EEM10.pdf
.Re
.\"
.Rs
.%B Total Commander: Supported cables for USB cable connection
.%I Ghisler Software GmbH.
.%U https://www.ghisler.com/cables/index.htm
.Re
.Sh CAVEATS
The point-to-point nature and additional latency of USB host-host links
makes them unsuitable as a "drop-in" replacement for an Ethernet LAN;
for a USB 3.0 SuperSpeed cable, latency is comparable to 100BaseTX Ethernet
(but often worse), with throughput comparable to 2.5GBASE-T.
.Pp
However, their energy efficiency makes them attractive for embedded applications.
A Plugable PL27A1 cable claims 24mA of USB3 bus power,
as compared to 150mA for a typical USB 3.0 to Gigabit Ethernet interface.
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 5.0 .
.Sh BUGS
The
.Nm
driver does not support the special packets described in section 5.1
of the CDC EEM specification.
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Doug Ambrisko Aq Mt ambrisko@whistle.com ,
.An Julian Elischer Aq Mt julian@FreeBSD.org
and
.An Nick Hibma Aq Mt n_hibma@FreeBSD.org .
.Pp
This manual page was written by
.An Nick Hibma Aq Mt n_hibma@FreeBSD.org
and updated by
.An Bruce Simpson Aq Mt bms@FreeBSD.org .
